To identify Parenchyma and Sclerenchyma tissues in plants from prepared slides - Lab Work

NOTE: The student doesn't need to write the procedure because they will be given the prepared slide however we are giving it for reference. The students only need to write the observation skipping the procedure part.

Aim

To study parenchyma and sclerenchyma tissues in plants from prepared slides.

Theory
Flowering plants are structurally complex as they are made up of different parts like roots, stem, leaves, flowers, fruits, etc. Each part is in turn an assembly of different types of tissues. Each tissue type has specific structure and performs a particular function. Plant tissues are broadly classified into meristematic and permanent tissues. Permanent tissues may be simple, permanent tissues like parenchyma, collenchyma and sclerenchyma. Complex permanent tissues are xylem and phloem. The structural features of tissues like wall characteristics, cell size, lumen size, and cytoplasmic contents are different in different tissues.

Procedure
Step 1: A tender stem of any of the herb is cut into bits of about 3 cm length and placed in water.
Step 2: A piece is hold between the thumb and forefinger in your left hand.
Step 3: A wet blade across the stem is passed in quick motion so as to get a thin, unbroken, circular cross section of the material.
Step 4: The process is repeated to get about fifteen transverse sections of the material.
Step 5: The sections is transferred to a petridish containing water. A thin, transparent section is selected and with a brush transfer it to a drop of water taken on a slide. Three drops of dilute safranin stain solution is added to the section and leave it for about five minutes.
Step 6: The excess stain is blotted. Three drops of dilute glycerine is added on the stained section. A cover slip is placed on it. It is then focused under the low power of microscope and observe the section.
Step 7: The section is focused under high power and observed again. The observations are recorded.

Observation

Sl. No.

Feature

Parenchyma

Sclerenchyma

1

Shape of cell

oval or spherical

elongated and polygonal

2

Arrangement of cells

loose

compact

3

Inter cellular spaces

present

absent

4

Lumen

absent

present

5

Nucleus

present

absent

6

Cell wall

present

present

8

Staining of wall

deeply stained

midly stained

7

Cytoplasm

present

absent

Results and Discussion
Parenchyma tissue is the most abundant type of tissue in plants. It forms the major bulk of stem, roots, leaves, fruits and seeds. The tissue is composed of living cells, with various shapes, sizes and functions. The cells provide mechanical support to the plant body. The parenchyma also acts as a storage tissue for food, air and water. Cells of sclerenchyma tissue are higly lignified with very thick cell walls and obliterated lumen. Cells are usually elongated and polygonal in shape in cross-section. The tissue provides the mechanical support and is found below the epidermis and around the vascular bundles.

Precautions
1. For sectioning, select soft, tender herbaceous stem only. Avoid stems that are hard and woody.
2. Take care not to injure your finger while sectioning.
3. Always keep the plant materials and sections in water.
4. Use dilute safranin stain solution.
5. The trachea and tracheids of xylem tissue appear to be very much similar to sclerenchyma and may be erroneously identified as sclerenchyma tissue. Xylem is always confined to the vascular bundle and is generally not seen in the cortex or pith.